由岁差常数求得的日月岁差是天文学的重要参数之一，它和地球动力学扁率相联系。地球动力学扁率的数值可 由黄经总岁差的天文观测得到，也可由地震观测建立的地球模型推求。地球动力学扁率在章动理论的计算中也是一 个重要的物理量。介绍了由不同的观测方法和模型给出的地球动力学扁率值，并讨论了它与岁差的关系和对章动计 算的影响。在刚体地球章动振幅的计算中，地球动力学扁率值起着尺度因子的作用，要改善刚体地球章动振幅的计 算，需要修改目前的黄经总岁差值。非刚体地球章动的转换函数中所采用的简正模频率和常数都直接或间接地依赖 地球动力学扁率值。在IAU 1980章动理论中，计算刚体地球章动振幅所使用的地球动力学扁率值与计算转换函数中 简正模频率和常数所使用的地球动力学扁率值并不一致。随着观测和计算精度的提高，地球动力学扁率值的不一致 将影响章动振幅的计算。在建立非刚体地球章动理论中，如何解释地球动力学扁率值的差异，如何选取地球动力学 扁率值，还有待进一步的研究。

The luni-solar precession, derived from the general precession in longitude, is one of the important parameters in astronomy. It relates to the Earth dynamical flattening which value can be obtained from the astronomical observation or from different Earth models. The Earth dynamical flattening plays an important role in the computations of nutation theory. Its values, determined from different kinds of observations and models are reviewed. Moreover, its relation to precession and its effect on nutation computation are discussed. The theoretical nutations of a non-rigid Earth are computed from a convolution of the rigid Earth nutation amplitude with a transfer function accounting for the geophysical parameters influencing the Earth rotation. The value of the Earth dynamical flattening correspounds to a scale in the rigid Earth nutation series. In order to improve the amplitudes of the rigid Earth nutation series, it become necessary to revise the IAU 1976 value of the general precession in longitude. The normal mode eigenfrequencies and constants adopted in the transfer function, depend directly or indirectly on the Earth dynamical flattening. The values of the Earth dynamical flattening, used in computing the amplitudes of the rigid Earth nutation series as well as the normal mode eigenfrequencies and constants of the transfer function, are not consistent in IAU 1980 nutation theory. The increasing accuracy of modern observations requires to take into account its influence on the nutation amplitudes at the level of a few microarcseconds. The interpretation and selection for different values of the Earth dynamical flattening will have to be approached in the construction of the future nutation theory of a non-rigid Earth.